Connectors of various types are known, and have been used, to grasp the ends of electrical conductors so they can be pulled through narrow passageways or conduits into the desired installation position. These conductors may typically have a diameter of between 1/4 and 3 1/4 inches, and may comprise the strands of a multi-strand cable, or mutually insulated strands of a multi-conductor cable, or entirely separate individually insulated wires or strands.
In many cases the connection must withstand severe pulling forces, for example as much as about 50,000 lbs. in some cases. Yet the connector should usually be as small as possible so it will be able to negotiate rather sharp bends in the conduit, for example the minimum 90.degree. elbow radii permitted by the National Electrical Code. Since the connector is usually applied in the field, when and as required by the particular installation, it should be as simple as possible to assemble, without requiring special or expensive tools or equipment. The connector parts themselves should be as inexpensive as possible, and reusability of at least some of the connector parts will contribute to reducing the expense of repeated cablepulling operations. It is also desirable in some cases to waterproof the devices by heat-shrinking a sleeve over it, particularly when the conductors are to be pulled through conduits contaminated with water, oil or mud.
Among the types of methods and apparatus for making such connections are swaged-type connectors such as disclosed in U.S. Pat. No. 3,673,313 of Wiley J. Pickett and Bynum E. Smith, filed Apr. 23, 1970 and issued June 27, 1972. While suitable for many purposes, the latter connector does require the presence on site of special high-pressure swaging equipment, and it is not generally feasible to re-use the connector parts.
Various other connectors are also known for making connections to the end of a cable, support wire, rope or the like using a wedge principal. Specifically in the art of boat rigging, it is known to use a steel connector made up of a split longitudinally-bored steel inner connector member having a conical outer surface, and a steel outer connector member having an inner longitudinal aperture the surfaces of which are conical with about the same taper as the exterior of the inner connector member. An outer layer of strands of a steel wire cable is disposed between the exterior conical surface of the inner conductor member and the inner conical surface of the outer connector member; the central strand is inserted into the central bore of the inner connector member. The inner connector member is then forced into the outer connector member by a screw-fitted cap, so that the outer strand layer is wedged between the conical surfaces of the inner and outer connector members, and the split inner connector is closed around the central strand. Also, at least some of the outer strands are additionally clamped between the cap and the inner connector member.
So far as is known to applicants, the latter boat-rigging technology has not been successfully transferred to the art of pulling electrical conductors. However, experiments performed by applicants have shown that if one attempts to apply this construction to the pulling of electrical conductors, (which are usually copper or aluminum, and therefore more soft and malleable than steel) there is a tendency under strong pulls for the conductors to be extruded and flattened between the hard steel surfaces on each side of them and to break more readily than desired.